Endoscopic suturing techniques and instruments have been developed to facilitate the suturing of tissue during endoscopic surgical procedures. Access to a surgical work site within a patient's body is normally provided through one or more portals formed directly in the patient's body or through one or more cannulas inserted into the patient's body through small incisions. A chosen surgical procedure is carried out by a surgeon through the use of elongated instruments inserted through these cannulas and it often becomes necessary to suture selected tissue at the surgical work site.
Since the work site is only accessible through a small portal or cannula and since it is very difficult to tie sutures within the body, various devices and techniques have been developed to enable the surgeon to tie sutures endoscopically. For example, some procedures enable the surgeon to pass suture material through selected tissue, form a surgical knot extracorporeally and then move the knot with a knot pusher through the portal or cannula into position adjacent the desired tissue to be sutured. Formation of the knot requires the surgeon to manually tie a knot on the suture strands after the suture is threaded through the selected tissues to be sutured. This procedure is often tedious and time-consuming. There is also a tendency for the knot to deform or collapse as the surgeon manually forces the knot down into its proper position. In addition, tying the knot in this manner is particularly difficult during endoscopic surgeries, where the visual field for the surgeon is severely limited by the narrow surgical area. As a result of these setbacks, there is a need for an improved method of tying a knot, as well as for surgical devices that will facilitate such method.